68 THE POPULAR SCIENCE MONTHLY. 



distinct reference to the habits and tastes of the fertilizing bees. It is 

 a mountain plant by origin, belonging to a tribe which took its rise 

 among the great central chains of Europe and Asia, and these Alpine 

 races are usually highly developed in adaptation to insect fertilization, 

 because they depend more absolutely upon a few upland species than 

 do the eclectic flowers of the plains, which may be impregnated hap- 

 hazard by a dozen different flies, or moths, or beetles. We can still 

 dimly trace many of the links which connect it with very simple and 

 primitive buttercups, if not directly, at least by the analogy of other 

 plants. For all the buttercup tribe show us regular gradations in the 

 same direction. The simplest kinds are round, yellow, and many-car- 

 peled, like the buttercups. Then those species which display their 

 sepals largely have dwarfed petals, like hellebore and globe-flower, or 

 have lost them altogether, like marsh-marigold, which trusts entirely for 

 color display to its big golden calyx. The still higher anemones have 

 the sepals white, red, or blue ; and the very advanced columbine has 

 all the petals spurred, and developed into nectaries, like those of monk's- 

 hood. But columbine still keeps to single terminal flowers, so that 

 here the five petals remain regular and circularly symmetrical, though 

 the carpels are reduced to five. Fancy a number of such columbine- 

 flowers crowded together on a spike, however, and you can readily 

 picture to yourself by rough analogy the origin of monk's-hood. The 

 sepals would now become the most conspicuous part ; the two upper 

 petals would alone be useful in insuring fertilization, and the lower 

 ones would soon shrivel away from pure disuse. Tbe development of 

 the hood and the lengthening of the upper petals would easily follow 

 by insect selection. It is a significant fact that our only other spiked 

 buttercup, the larkspur, has equally irregular and bilateral flowers, 

 though its honey is concealed in a long spur formed by the petals, and 

 accessible to but one English insect, the humble-bee. Knowledge. 



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ON THE COLORS OF WATER. 



By M. W. SPRING, 



OF THE tTNIVERSITY OF LIEGE. 



YIEWED in relatively shallow masses, clear water appears wholly 

 colorless. In our daily dealings with the liquid we seldom have 

 occasion to observe it in great depths ; hence it has been generally 

 believed that water is quite destitute of color. The ancients were 

 accustomed to explain the transparency of some bodies by assuming 

 that they partook of the nature of water ; and we now speak of a 

 diamond as of the first water, to emphasize its perfect transparency and 

 colorlessness. If, however, we regard the larger masses of water in 



